This invention is related to resilient valve seats for ball valves, gate valves, etc., wherein the seat member is deformed by the valve member upon assembly of the valve and it is additionally resiliently deformed during pressure loaded conditions to insure positive sealing. To be more specific, this invention relates to valve seats which in a preloaded condition maintain a relatively small surface contact with the valve member and in a pressure loaded condition the downstream seat member in a valve has a substantially larger contact surface area.
In many prior art valve constructions, the seat members are placed under a load which establishes the initial seal for the valve by placing the seat member in substantially a full seat surface contact with portions of the valve body and the valve member(s) so that initial loading and further pressure loading of the valve seat member(s) additionally compressibly load the seat members. In such typical valve constructions where the seat member is restrained a substantial interference develops between the seat member and the valve member with the resultant force acting against the valve member and requiring high forces to move the valve member on the seat member in either opening or closing the valve. Additionally, it is to be noted that because these typical prior art seat construction maintain a generally full surface seat contact, the resultant interference forces are at least a minimum when the valve is open and the seat members are only under the influence of preloading forces. These prior constructions are particularly unsatisfactory because relatively high forces are created by the full seat contact surfaces and thus large forces are always required to move the valve member.